In order to limit the value of the maximum torque that can be transmitted between the output shaft of the electric motor and the starter output shaft which carries the starter head, it is known per se to provide a torque limiting device. For this purpose it has previously been proposed, for example in Japanese patent specification JP 06/078 495A, to provide a starter in which the epicyclic gear train comprises a cylindrical casing, in which the crown, which has an internal set of teeth, is mounted for rotation, the starter being of a type in which the crown wheel is coupled in rotation to the casing through a torque limiting device of a friction type which is interposed axially between the crown wheel and a transverse plate of the casing.
In that document, the friction ring comprises an annular friction disc which is coupled in rotation to the crown wheel, and which is in axial engagement against the internal face of one of the transverse plates of the casing, against which the friction disc is biased axially by a frusto-conical ring. That design therefore calls for at least two additional components, as compared with an epicyclic gear train having no torque limiting device, that is to say the friction ring and the frusto-conical resilient ring.
Apart from the large number of components involved, the design proposed in the above mentioned Japanese patent specification complicates the design of the crown wheel of the epicyclic gear train, increases the overall axial size of the epicyclic gear train, and makes the assembly of the different components of the starter particularly complex.